1. Field of the Invention
This invention relates to container structures, and more particularly, to large hoppers adapted for mounting on a mobile platform for facilitating the distribution of pulverulent solid fertilizer.
2. Brief Description of the Prior Art
Dry fertilizer has heretofore been widely used in agriculture. For the purpose of distributing fertilizer granules or pellets over a large area, mobile vehicles have been provided which carry upon a rearwardly extending bed, a steel container or hopper which is generally configured as a frustum of an inverted pyramid having upwardly extending side walls and end walls secured to the upper edges of the convergent frustoconical walls of the lower portion of the hopper. Extending along the bottom of the hopper in a position to receive the fertilizer pellets therefrom is an endless belt conveyor which functions to move the fertilizer through a metering gate located at one end of the hopper. After the fertilizer passes through the metering gate on the endless belt conveyor, it is discharged onto a pair of rotating spreader or spinner plates which carry blades functioning to throw or propel the fertilizer pellets outwardly over a large area as the vehicle moves forward.
The gauge of steel plate from which fertilizer hoppers of the type described have previously been made has, of necessity, been such that although the hopper is relatively heavy in its overall weight, the thinness of the plates permits them to become more easily bent and buckled over extended periods of usage when the hopper is loaded to capacity. It is also characteristic of the metal from which the hoppers have been previously constructed that the metal becomes corroded and weakened by contact with the alkaline chemicals of the fertilizer as residual amounts of the fertilizer remain in the hopper and become dampened by rain or moisture. This corrosion of the walls of the hopper requires relatively frequent maintenance during which the walls are sandblasted and repainted. Moreover, over a relatively short operating life span, the thinness of the metal due to the corrosion and refinishing described becomes such that the hopper must be replaced.
In prior constructions of fertilizer hoppers of the type described, the fertilizer supporting upper run of the endless belt conveyor has passed over a series of horizontally spaced angle irons which extend across the bottom of the hopper between the runs of the conveyor belt. When the belt is loaded with fertilizer, the belt tends to develop a catenary or sag between the spaced angles, and a substantial amount of drag, as well as frictional wear, is developed as the belt slides across the angles during its horizontal movement for discharging fertilizer. Moreover, a very marked tendency has existed in prior constructions for excessive drag to be developed at such time as any moisture accumulates on the lower surface of the upper run of the conveyor belt due to the sticking tendency of the belt as it passes over the spaced angles which have been described. The drag imposed by this sticking tendency on the motor used to actuate the belt shortens the service life of the motor, as well as developing excessive stress on other mechanisms employed in the conveyor system. This propensity for excessive dragging when moisture accumulates on the lower surface of the conveyor belt is amplified in those instances where a flat steel plate is used as the bottom of the hopper and is positioned beneath the fertilizer supporting run of the belt.